1. Field of the Invention
This invention relates to the air filtration art, and, more particularly, to a self contained unit for providing air filtration of ambient air in enclosed spaces such as rooms and vehicles.
2. Description of the Prior Art
Air pollution has existed since the beginning of man in the form of dust, smoke, pollen, odors, viruses, molds, and bacteria. In the past only hay fever sufferers were seriously inconvenience by air pollution. Now in our increasingly crowded environments pollution levels of all the above pollutants have increased along with new additions such as insecticides, chemicals, and smog. It is no longer possible to simply open a window to let clean air enter. The outside air is usually dirtier than the inside air. In addition, cooling and heating energy costs have increased dramatically to the point that windows must be kept closed in order to retain the cooled or heated air inside no matter what pollutants may remain inside.
Generally, almost all present air filtration methods are incorporated as a part of central air conditioning and/or heating systems. Filtration media is placed in the return air ducts which travel from the floor or baseboard of a room to the cooling and heating equipment. Conditioned air is then returned to the room through ducts near the ceiling. The air filtration media placed in these systems is almost universally of the fiberglass furnace type or foam air conditioner type. Neither removes particulates below the size of lint and dust. Homes without forced air heating and/or cooling usually do not have any air filtration equipment at all.
Some central systems have electronic air cleaners installed which remove virtually all particulates including smoke, pollen, dust, viruses, molds, and bacteria but they do not remove gaseous pollutants such as odors, smog, and chemicals. In addition, electronic air cleaners create ozone which is irritating to many parts of the human body as well as plants and animals.
A few thousand homes in the Los Angeles, Calif., area have activated carbon air filters which remove gaseous air pollutants by the adsorbtion properties of the activated carbon. Activated carbon for air filtration is used in other locations only for highly specialized purposes such as to clean the air in submarines, space capsules, high flying aircraft, computer rooms, and in special industrial clean room situations including apple and flower storage facilities. Activated carbon is also the major active ingredient in gas masks.
Room air cleaners which plug into wall electrical outlets generally incorporate small electronic air cleaners followed by activated carbon filters. Most of the ozone produced by the units is removed by the carbon filters. These air cleaners are either placed on tables or sit on the floor with the clean air being ejected out of the back of the units at approximately waist height in a horizontal air flow pattern. The clean air mixes with the dirty air with no cyclical air flow pattern being achieved as is found in central air conditioning and heating systems. Eventually most of the pollutants in the ambient air in a given enclosed air space do pass through the electronic air cleaner where they are trapped.
Several room air cleaner systems have been developed which utilize activated carbon either alone or in conjunction with high efficiency particulate filters to clean the air. All of these units exhaust the air out of the back or side in a horizontal pattern thereby mixing the clean air with the dirty air in the room. The high efficiency particulate air filters in these units have approximately the same efficiency range as do the electronic air cleaners. The great advantage of the activated carbon units is that the proportion of carbon in these units is a multiple of that in the primarily electronic air cleaners discussed immediately above. The activated carbon air filters included with the electronic air cleaners are designed to simply bring the ozone produced by the electronic air cleaners down to an acceptable level. No extra activated carbon is included to remove gaseous pollutants other than ozone.
Conversely, many activated carbon room filter units have only activated carbon filtration media and no particulate filtration capability at all. These units are primarily found in hospitals where odor is a problem and in flower shops where plant decay must be minimized.
All activated carbon room filter units that do have particulate filters have them as separate filters located apart from the activated carbon. The usual configuration is to place a furnace type particle filter in front of the activated carbon media. One unit made by Aireox Research in Riverside, Calif., wraps a high efficiency particulate filter around the outside and inside of a cylinder containing activated carbon and retains the filter material in place by the use of cardboard and staples. The resulting arrangement is expensive to manufacture and must be thrown away when it is dirty. Another form of air cleaner has recently appeared on the market in the form of air ionizers. The ionizers emit negative air ions which discharge when they hit floating particulate matter which usually carries a positive charge. When the particulate matter become neutral in charge, it loses its ability to remain floating in the air and falls to the floor. The major problems with air ionizers as air cleaners is that they are effective only for limited areas and the pollutants which do fall out of the air simply fall to horizontal surfaces where they may be easily stirred up again and reintroduced into the air.
Thus, all existing room air filters have severe deficiencies. All known prior art air filter units other than air ionizers for use in rooms disperse the clean air in a horizontal pattern which mixes readily with the surrounding dirty air. Not only does this arrangement delay the cleaning of the air but it also blows particles off horizontal surfaces thereby reintroducing them into the air again. The activated carbon room units that do have particulate filters make do with existing expensive particulate filter assemblies or attach them in expensive configurations separated from the activated carbon.